Just my two cents ...
For Catholics, dating implies seeking a potential spouse. Age ranges are a personal issue when seeking a spouse, however, generational barriers are ,real and genuine. When someone is young enough to be your daughter or son, or old enough to be your father or mother, there is a social barrier there - it may not be acceptable to everyone.
Those barriers aren't just numbers, they are a set of experiences (or lack thereof) that shapes personality, outlook, behaviours and future plans. The generational differences put people in different places in life - there is big difference between wanting to start college and enjoying going to the movies with your friends and dealing with the trials and tribulations of first job experiences and someone who is planning for retirement in a few years.
Age differences that are less than a generation are generally more socially acceptable because the life experience gap is not so huge. A husband and wife are partners in life. A husband is a wife's husband, he is neither her father nor her son; a wife is a husband's wife, she is neither his mother nor his daughter.